Urban Protocol Bundle - Earth as a System

• Atmosphere
  • Air Temperature
    • Concrete and buildings found in cities and towns affect how much heat is radiated away from the Earth. This irradiated heat can affect local air temperatures which have cascading effects for other parts of the environment.
  • Clouds
    • The cloud cover over a city affects the land-air energy budget through many different parameters, like surface temperature, relative humidity, and precipitation. Conversely, cities can also affect the formation of local clouds by limiting evaporation and vegetative transpiration rates. 
  • Precipitation
    • Areas covered with artificial, impervious materials like concrete or asphalt can experience higher flood risks from precipitation than more natural spaces.
  • Surface Temperature
    • Surface temperature is an important parameter for assessing the presence and intensity of the surface urban heat island. It's an essential factor for the estimation of the energy budget in an urban area because it controls the heat transfer from the ground to the air—also known as sensible heat. 
  • Relative Humidity
    • Evaporation acts as a cooling mechanism for cities. However, impervious urban materials, like asphalt and concrete, don't retain water, so evaporation rates from surface and subsurface soils are drastically limited. Lower evaporation rates also impact the overall relative humidity in an urban environment. 
• Biosphere
  • Biometry
    • By measuring the heights of the tree and vegetation canopy in urban environments, we can better understand how variables like surface temperature, humidity, and building heating loads are affected by greater or lesser amounts of natural shade.
  • Land Cover
    • Since cities replace natural, vegetative land cover with harder surfaces, it's important to know how these changes in material affect local temperatures, albedo, emission coefficients, and the land-air energy budget. This knowledge also helps guide us on the least ecologically impactful way to expand our urban environments.
• Hydrosphere
  • Water Temperature
    • The temperature of urban water bodies influences amount of airborne water vapor, and thus humidity, cloud cover, and precipitation. Higher temperatures typically lead to higher evaporation rates, while lower temperatures have the opposite affect.
• Pedosphere (Soil)
  • Soil Characteristics
    • The characteristics of urban soil are greatly influenced by human activity. For example, the materials comprising the soil can change significantly from their original form after a building or road construction project begins.   
  • Soil Infiltration
    • Impervious urban materials typically have lower water infiltration rates, which can lead to higher risk of flooding after extreme precipitation events. 
  • Soil Moisture (Gravimetric)
    • Through anthropogenic changes to land cover, soil characteristics, and the atmosphere, we are directly affecting the soil moisture content in urban areas. The water content of the soil has a significant impact on the areas biome type as well as the plants/animals that can live in that area. 
  • Soil Temperature
    • By converting natural landscapes into urban ones, we affect the temperature of the soil beneath us. Changes in the soil's temperature has broad impacts on the underground ecosystem, and thus the environment on the surface.

Check out our chart below for a visual representation on how all these protocols fit together within the Urban Bundle: 
 

Urban areas comprise less than 3% of the Earth’s surface, however their proliferation has been largely driven by socio-economic factors with little consideration for their environmental impact. Today, a particularly important aspect for studies of urban environments is the lack of balance between natural and built spaces. These imbalances influence a host of other factors including, urban microclimatic changes, the depletion of green spaces, increases in anthropogenic heat sources, proliferations of impervious sources, deteriorated air quality, increase flooding and much more.

Air pollution and heat islands within urban ecosystems are especially crucial areas of study due to their negative impacts on human health. Air pollution impacts are exacerbated for members of vulnerable groups, while increased temperatures lead to more energy used for cooling. The latter can lead to poor city energy efficiency, intensified energy poverty, and greater disparities between socio-economic classes.

These two issues are mostly confined to medium- and large-size cities. However, the differences measured between urban and rural area can be quite significant. For example, air temperature measurements can raise by 6-8 degree Celsius as you move from the countryside into the built environment. Furthermore, poor urban planning can lead to temperature variations within the city itself, creating areas of excessive thermal intensity.

This intensified thermal heating is a result of the change in natural green spaces to hard environments with significant heat loads. Where forests or fields would cool the local area through evapotranspiration processes, urban settings lack the moisture to adequately cool the habitat through the same methods. Additionally, buildings have a strong impact on the flow of wind through the area and, in most cases, suppress the outgoing thermal radiation close to the ground.

Urban population worldwide has grown rapidly from 751 million in 1950 to 4.2 billion in 2018. Asia, despite its relatively lower level of urbanization, is home to 54% of the world’s urban population, followed by Europe and Africa with 13% each. Today, the most urbanized regions, with percentage of population living in urban areas, include:

• Northern America: 82% 
• Latin America and the Caribbean: 81%
• Europe: 74%
• Oceania: 68%

*Measurements from 2018

The level of urbanization in Asia is now close to 50%. In contrast, Africa remains mostly rural, with 43% of its population living in urban areas. Overall, 55% of the world’s population lives in urban areas, a proportion that is expected to increase to 68% by 2050. 

Given these increases in urbanization, it's important to ensure that the natural ecosystems in our cities are in good condition. To support this effort, you can take action by examining the state of the environment in the city where you live and try to identify the parameters that influence the quality of life for city dwellers. You can also help raise awareness of urban ecosystem problems by reporting your findings to our databases and other environmental authorities to better understand how the urban habitat affects the various Earth spheres.